High-Yield Exfoliation of Monolayer 1T’-MoTe₂ as Saturable Absorber for Ultrafast Photonics

Abstract

Liquid-phase exfoliation can be developed for the large-scale production of two-dimensional materials for photonic applications. Although atomically thin 2D transition metal dichalcogenides (TMDs) show enhanced nonlinear optical properties or photoluminescence quantum yield relative to the bulk phase, these properties are weak in the absolute sense due to the ultrashort optical path, and they are also sensitive to layer-dependent symmetry properties. Another practical issue is that the chemical stability of some TMDs (e.g., Weyl semimetals) decreases dramatically as the thickness scales down to monolayer, precluding application as optical components in air. To address these issues, a way of exfoliating TMDs that ensures instantaneous passivation needs to be developed. Here, we employed a polymer-assisted electrochemical exfoliation strategy to synthesize PVP-passivated TMDs monolayers that could be spin coated and restacked into organic− inorganic superlattices with well-defined X-ray diffraction patterns. The segregation of restacked TMDs (e.g., MoS 2 ) by PVP allows the inversion asymmetry of individual layers to be maintained in these superlattices, which allows second harmonic generation and photoluminescence to be linearly scaled with thickness. PVP-passivated monolayer 1T'-MoTe 2 saturable absorber fabricated from these flakes exhibits fast response and recovery time (<150 fs) and pulse stability. Continuous-wave mode-locking based on 1T'-MoTe 2 saturable absorber in a fiber ring laser cavity has been realized, attaining a fundamental repetition rate of 3.15 MHz and pulse duration as short as 867 fs at 1563 nm.

Structural Evolution of Atomically Thin 1T’‐MoTe2 Alloyed in Chalcogen Atmosphere

“…Characteristic Raman vibrational modes for 1T'-MoTe 2 are largely diminished for unprotected samples after exposure in air for 1 h (red curve in Figure 8h). These phenomena agree well with Te-based TMD atomic layers either exfoliated or CVD prepared in the previous experimental reports, [14,34,[62][63][64] confirming universal vulnerability of this type of 2D material in oxygen atmosphere.…”

Electronic, Optical, and Magnetic Properties of Doped Triangular MoS2 Quantum Dots: A Density Functional Theory Approach

“…However, we speculate about the possibility of determining the values of refractive index from experiments involving TMDQDs in diluted solutions, such as recently reported. [60] From the structural point of view, the comparison with the case of a pristine MoS 2 ML indicates slight changes in the Mo-S distance, while the S-S one shows a small increase in QDs.…”

“…However, we speculate about the possibility of determining the values of refractive index from experiments involving TMDQDs in diluted solutions, such as recently reported. [ 60 ]…”

Robust Lithium–Sulfur Batteries Enabled by Highly Conductive WSe2‐Based Superlattices with Tunable Interlayer Space

“…The presence of the PVP molecular layer effectively separates the WSe 2 stack, shifting the (002) peak/spot in the XRD and electron diffraction patterns. [ 38,39 ]…”